Power Automate and Bookings - update an appointment duplication

Hi there

I am fairly new to PowerAutomate, but have a couple up to work with MS Bookings; one to add a row when an [group] appointment is created, and one to add a row when an [group] appointment is updated (in Excel).

However, the "update an appointment" adds all the people in to the list again who are in already in the appointment, not just adding the extra person on the end who has added themselves to the group booking.  For example, how do I stop the [DUPLICATE] entries in the example below:

I have these Flows (similar for when an Appointment is Created):

If I take the "Apply to each" out, it creates errors.  I just want the [NEW] entries in my example, and not the [DUPLICATE]s added again!  Many thanks in advance.